Questions tagged [hvac]

(Heating, Ventilating, and Air Conditioning) For questions about installing, repairing, and troubleshooting HVAC systems.

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HVAC recommendation

When renovating a split/multi-level house, with four separate living levels and a total of 10 rooms, what is the best method of heating and cooling without replacing floors? Existing is a combination ...
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Blaring noise from newish indoor AC unit

Why is my AC making a noise like Mass Effect Reaper every 20-60 seconds and how can I stop this? https://webmshare.com/play/qd07r
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57 views

There is a pvc pipe that goes into my floor next to my water heater and central ac unit and its overflowing..but why?

Let me start by saying i'm not a plumber nor have i done HVAC. Last night i walked in and noticed I've have a leak in the corner of my living room so i looked for where it was coming from and on the ...
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1answer
7 views

Air conditioner HVAC filter size and frequency of change

I've been struggling to understand air filter sizes and the frequency of changing them out. We have a Rheem 4 ton AC unit. Below is the filter (20x25x4) we currently have in our attic and some info ...
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AC blower turns on and off 1 or 2 times per second

I have a Carrier Weathermaker 8000. When using the A/C and the house is below the temperature called for by the thermostat, the blower motor randomly turns on and after 10 seconds or more will start ...
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Can't get 24v to outside unit

I have a gmp100-4 furnace. Had thermostat, board, abd transformer replaced. Everything is working but can't get 24v to the outside unit. I'm afraid they hooked up something wrong. All started from ...
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HVAC blower comes on by itself. Even after I remove the thermostat wires

I have a rheem classic 90 furnace/AC. From the past one month, I am noticing that my blower fan turns on, runs for 2 mins and then turns off when thermostat is off. Also, when running the air ...
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1answer
23 views

Blown Thermostat Twice and Dead Transformer

A year ago, I had a brand new smart thermostat that caused the A/C fuse to keep blowing. I replaced the thermostat with a duplicate, swapped the fuse out and everything has been fine. Now a year ...
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Relocating Return Air Duct and Determining Register Box Size

I have a 14-inch diameter return air duct that I'm relocating. The duct was formerly connected to the floor where a roughly 16 x 15 inch hole had been cut from the subfloor to let air get to the ...
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Should I move an HVAC vent to the ceiling or on the opposite interior wall?

The below picture shows the current position of the vent (the white area over the sink). The blue patch above the toilet is a small window. The plan is to relocate the bath tub and position it along ...
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Do I need OEM filter replacements for a whole home media air purifier?

I purchased a home that had a media air purifier already installed. Specifically, it is the TopTech TechPure TT-MAC-2025 (installation manual). The manual specifies the filter should be #TT-FM-2025(...
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1answer
37 views

What's the best way to relocate my wall vent?

I recently removed a closet in our main living area and one of the closet walls contained an AC supply vent. This left a 4x12 hole in the floor where the old stack head was removed. While we could ...
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1answer
21 views

Adjusting ECM motor air flow

I recently had the following Rheem ROCB furnance installed. https://www.rheem.com/product/ROCB-118P05-M It's paired with a Rheem 5 ton condenser for cooling. However, I feel the air flow is set way ...
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112 views

AC not shutting of automatically

I recently had new HVAC installed. I am noticing it being little louder than what I had previously. The new system is American Standard 80% efficiency with ECM blower motor. My question is Can I ...
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2answers
52 views

AC leaking into drip pan in the attic

I apologize in advance for this long post. This is the first summer in this home that I bought. I'm a first time homeowner. One day I realized a big stain in my ceiling right under the attic and found ...
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1answer
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Exposed wires to HVAC unit from house

I was mowing my lawn today and noticed that some of the wires running from the house to the HVAC unit were exposed. It looks as if something chewed off what surrounds the wires or it was caught by the ...
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1answer
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Can I use hot water to transfer heat from a greenhouse into the house?

We have a vacation house that has a (south-southeast facing) greenhouse off of one of the bedrooms. On a sunny day in winter, the greenhouse can easily reach 80F or more. When we are there, we open ...
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Is my brand new central air conditioner short cycling?

I just had a brand new air conditioner 5 ton condenser, coil and furnace installed in a 3,300sqft colonial in Connecticut. It’s 1am right now, 75 degrees outside with 97% humidity. I have my upstairs (...
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ECM Blower Motor Not Working at Night

So, I have had this problem going on for about a month and a half now with my A/C. Throughout the day, the A/C will work fine. However, there will come a time in the middle of the night when it ...
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39 views

Condensation on HVAC, mold on joists/subfloor in basement

I have heavy condensation on the plenum and supply line near an exterior wall/window in my unfinished basement. I have mold and moisture on my subfloor and joists just in this 3 sections. I sealed up ...
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2answers
64 views

Should my ground-level package unit have a condensate drain trap?

I recently got a new package unit installed to replace the 30-year-old one that came with the house. It works MUCH better than the old one, which had a slow leak and iced up regularly. I noticed that ...
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1answer
22 views

What is the deltaT test for a PTAC AC?

I have a PTAC AC that blows cold air, but barely cools the room. The landlord is claiming its because the room is the livingroom and its an open to the kitchen and hallway. I know that the rule of ...
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1answer
20 views

What would cause my line sets to equalize in cooling mode?

My heat pump line sets only get different temperatures briefly on startup in cooling mode. Then the hissing noise stops and they equalize and only the lower 1/4th of the a-coil gets cold and ...
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1answer
20 views

Leak check mini split AC

I am finishing up a 6 zone mini split DIY installation and before closing up some of the walls I would like to do some leak checks. My set up is that from the condenser it splits into 2 branch boxes ...
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1answer
33 views

connect switch handy box to plenum?

would it be code to attach the 2 x 4 handy box with the switch on the plenum as the old furnace set up would hook up on the new furnace with the bx cable coming off bottom of handy box to furnace ...
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Two air handlers, one furnace, and an odd control system. What's the modern equivalent?

I have 2 air handlers, each has their own AC, and each of them have a hydronic heat coil that leads to one furnace. Air conditioning works well independently, but there's some weird controls when it ...
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1answer
57 views

Is the purple wire on AC blower motor common wire?

I’m replacing my AC blower motor. The old one had Red,Blue, Black wires for speeds, white Common, and brown & brown/white wires to the capacitor. (Yellow, purple wires for rotation). The new motor ...
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How is an air handler's fan controlled if its control board doesn't have a G terminal?

Background I have a 2-stage cooling heat pump unit from Bryant, installed ~2006 (central Florida): Condenser model 698BNX048-B Handler model FE4ANB006 Shortly after moving in ~5 years ago, our evap ...
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Can I add a thermostat C wire to my furnace's control board if there's already a wire under the screw? [duplicate]

I bought a new WiFi thermostat and it requires 5 wires and I only have 4 currently. I will run a new set of wires from the thermostat to board, however on the board it shows that I have a C wire but ...
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1answer
92 views

Why aren't phase-change heat pipes more common in homes?

Laptops contain very efficient heat pipes, which can transfer heat over long distances with extremely low thermal resistance, hundreds of times more efficiently than pure copper. It seems to me that ...
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1answer
30 views

Mini split minimal pipe length

Quick question - my LG mini split manual says that I need a minimal of 10’ from the indoor unit to the branch box. My question is do I include the 1-1.5’ piping that comes with the indoor evaporator? ...
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2answers
89 views

Is #10 wire correct for my mini-split system on a disconnect?

I have a disconnect box that is on a 50 amp breaker connected to a disconnect box using 6 AWG. In order to connect my mini split system to the disconnect do I use 10 AWG wire based on the information ...
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1answer
77 views

Open duct found in ceiling

I cut a hole in a basement ceiling drywall and found an open duct at the end of the span between the joists (see photo). I'm sure this isn't good for the efficiency of the hvac system. What are the ...
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2answers
41 views

Help adding relay for thermostats

My nest thermostats are missing a common wire which means they’re not getting enough power to work properly. I actually didn’t realize this until an electrician told me about it (it hadn’t become a ...
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Home A/C Unit making startup noise

Our home A/C unit makes several short (~5 seconds) humming noises before actually starting up. I was wondering if this is normal? It works fine otherwise and it usually only does it a couple of times ...
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21 views

vinegar for Trane furnace

I installed a new gas heater with a condensing unit in 2019 winter. Here is the detail. My question is... Every year, I'd better pour some vinegar after opening the cap of the picture? If yes, how ...
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31 views

heat pump air handler blower motor stalls at start up randomly

The air handler blower sounds like it is being switched off and on rapidly but will eventually run. This occurs randomly at start up. Most of the time it starts and runs fine. Could the capacitor be ...
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Inconsistent damper control and ventilation control settings

While changing my dual-zone HVAC system's filters I noticed a lack of consistency in damper control and ventilation control settings. There are two of each type of control. The first damper control ...
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1answer
35 views

Central Air condition system isn't working

replaced thermostat and capacitor and transformer, heat turns on and blower turns on. I have power to the switch board with no fault lights. The A.C. itself won't turn on? Weather King Unit, I'm not ...
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1answer
50 views

Does lengthy refrigerant line between indoor and outdoor unit affect AC performance and result in higher utility bill?

As part of basement renovation, I am moving the HVAC indoor unit for about 30 feet, which means the refrigerant line has to be extended by same length concealed within basement ceiling. Now, I have ...
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2answers
63 views

Why is there a musty smell from my HVAC system even after coil cleaning?

I am having trouble getting rid of a smell in my AC (installed 2016), 2 visits by an HVAC professional have resulted in no luck. Problem: There is a musty smell, from all vents, as the AC is turning ...
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1answer
88 views

Why is there condensation on a pipe near my furnace?

My AC says it is trying to cool to 73 but is reading 75. I changed the filter, which didn't help. I looked in the closet, and apparently the installers were supposed to install an "auxiliary ...
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1answer
93 views

Sewer smell in bathroom ONLY when central a/c is on and kitchen sink is running water

This is a weird one, and have come across multiple handymen and none of them can pinpoint the problem when I describe it. Though they have never been in the room when it happens. Here is the scenario.....
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2answers
68 views

Outdoor disconnect for central air plus mini-split

We are arranging with an HVAC pro to replace our central AC compressor and add a separate mini-split system. We will have two compressors in close proximity on the side of the house where we presently ...
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2answers
48 views

How to solve Hot Upstairs but cold basement

I have central air in my house(20 year old house). In my basement it gets cool, and cold air is coming from a vent in the ceiling. My upstairs gets really warm and humid even though central air is on. ...
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2answers
40 views

how To Silence a Loud PTAC AC Unit?

I moved into an apartment with a loud (and somewhat not so cooling) PTAC in-wall AC unit. Each room has its own, a total of 3. The land lord is super cheap and only replaced the 8+ year old unit in ...
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HVAC / Furnace Evaporator unit in attic leaking cold air

We have an A/C (and heat) unit in the attic with force air ducts going to the ceilings in the rooms. I was in the attic today when the A/C turned on. I felt cold air come on my leg when I was near the ...
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1answer
30 views

Curtains to direct airflow

All the cold air from my AC flows through a stairwell and into the basement. The entrance to the basement is the through a doorless opening on the 1st floor. I am planning to put up a curtain in that ...
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26 views

Help reroute cold air return

I am working on opening up space between my lobby (on the right side of the wall) and the dining room area (on the left side of the wall). The section of the wall that is used as cold air return ducts ...
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2answers
71 views

Should air be escaping from this?

I have a Rheem Criterion Gas Furnace. At the moment, my air conditioning system currently has low air pressure coming from the vents around the house. I double checked that the fan is working, ...

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